Acquisition - Business Acquisition Purchase Price Allocation Assets Acquired and Liabilities Assumed (Detail) (USD $) In Thousands, unless otherwise specified	6 Months Ended	12 Months Ended
	Jun. 30, 2014	Dec. 31, 2013
Business Acquisition [Line Items]
Value of Quanta common stock and exchangeable shares issued	$ 38,641	$ 88,895
Cash paid	83,200	341,100
All Acquisitions [Member]
Business Acquisition [Line Items]
Value of Quanta common stock and exchangeable shares issued	38,641	88,895
Cash paid	83,242	341,064
Fair value of total consideration transferred	121,883	429,959
Current assets	53,174	193,895
Property and equipment	33,445	60,988
Other assets	3,374	1,009
Identifiable intangible assets	22,368	55,124
Current liabilities	(41,283)	(127,430)
Deferred tax liabilities, net	(3,604)	(4,083)
Other long-term liabilities	(3,935)	(5,350)
Total identifiable net assets	63,539	174,153
Goodwill	58,344	255,806
Fair value of total consideration transferred	$ 121,883	$ 429,959